Sialodacryoadenitis (SDA) is an infectious disease of rats with a high morbidity and low mortality. The principal organs affected include the eye, harderian and exorbital glands, and submaxillary and parotid salivary glands. Our laboratory has isolated an agent tentatively classified as a corona virus which can induce the disease complex in either germfree or serologically negative SPF rats. Our objectives include extending this work to further define and characterize the etiologic agent biologically and antigenically, study the pathogenesis of the ocular lesion, further refine serological methods now employed with this agent, study the natural history of the disease in individual animals and in colonies, determine the natural mode of transmission and propagation of the disease in rat colonies, and develop rational control procedures based on sound scientific data. One additional objective may be the development of a suitable vaccine for colony control of SDA. Methods employed will be standard virological techniques well established in our laboratory combined with histopathology, electron microscopy, clinical chemistry, clinical medicine, and epidemiology.